Water has long been recognized as one of the earth's most precious resources. Recent scientific reports have indicated that the population of the earth may double by the year 2050, placing severe stress on the supply of fresh water available for human use, crops, livestock and other needs where only relatively clean water is acceptable to meet the requirements. In many areas, the demand for fresh water already exceeds the supply, and the situation is only expected to worsen. Desalinization is not always an option, because it ordinarily requires that a nearby source of salt water be available. Cost also continues to be comparatively excessive. Desalinization is customarily confined to areas where fresh water is either scarce or unavailable.
Many industrial uses of water result in contamination with volatile organic compounds (VOC's) such as oils, gasoline, benzene, etc., to the extent that the degraded water is no longer fit for other purposes. A number of methods of treatment of VOC-contaminated waste water have been in use for a considerable period. They typically involve aerating the waste water to cause separation of the VOC's from the water by providing for their molecular attachment to air, discharging the separated VOC's and air and letting the water flow by gravity or by being pumped to a collection point for the now-decontaminated liquid Examples of apparatus for practicing the method are illustrated in U.S. Pat. Nos. 4,544,488, 5,266,208, 5,470,478, 5,685,976 and 5,069,796. This prior art demonstrates various types of towers and tanks in which forced air is passed upwardly through descending water moving by gravity from one perforated, shallow tray to another or through a bed of particulate material, ordinarily by bubbling the air through the water from below to create a froth of the contaminant, and then separately collecting the then-contaminated air and decontaminated water. Other of these systems utilize charcoal or carbon to finally adsorb the last-remaining organic materials when the water is to be stripped completely of contaminants. Typically, while such systems are effective to one degree or another, they generally suffer to some extent from being labor-intensive in requiring frequent disassembly and cleaning and from being complex in structure. Obviously, decontamination of a processed liquid cannot be performed satisfactorily by equipment that collects contaminant internally during processing and retains some of the contaminating substance within the equipment after processing. None of the equipment of the above-mentioned prior art systems can be said to be self-cleaning.
Additionally, it is typical to provide demisting apparatus with conventional air strippers, increasing the overall cost of the equipment and necessitating that the demisting means also require periodic disassembly and cleaning.